From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg KH Subject: Re: [PATCH] 8250: Hypervisors always export working 16550A UARTs. Date: Thu, 28 Apr 2016 15:56:33 -0700 Message-ID: <20160428225633.GA9134@kroah.com> References: <1461881913-23967-1-git-send-email-rjones@redhat.com> <1461881913-23967-2-git-send-email-rjones@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1461881913-23967-2-git-send-email-rjones@redhat.com> Sender: linux-kernel-owner@vger.kernel.org To: "Richard W.M. Jones" Cc: jslaby@suse.com, peter@hurleysoftware.com, andriy.shevchenko@linux.intel.com, phillip.raffeck@fau.de, anton.wuerfel@fau.de, yamada.masahiro@socionext.com, matwey@sai.msu.ru, valentinrothberg@gmail.com, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, ddutile@redhat.com List-Id: linux-serial@vger.kernel.org On Thu, Apr 28, 2016 at 11:18:33PM +0100, Richard W.M. Jones wrote: > Currently autoconf spends 25ms (on my laptop) testing if the UART > exported to it by KVM is an 8250 without FIFO and/or with strange > quirks, which it obviously isn't. Assume it is exported to us by a > hypervisor, it's a normal, working 16550A. > > Signed-off-by: Richard W.M. Jones > --- > drivers/tty/serial/8250/8250_port.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c > index 00ad2637..de19924 100644 > --- a/drivers/tty/serial/8250/8250_port.c > +++ b/drivers/tty/serial/8250/8250_port.c > @@ -1171,6 +1171,13 @@ static void autoconfig(struct uart_8250_port *up) > if (!port->iobase && !port->mapbase && !port->membase) > return; > > + /* Hypervisors always export working 16550A devices. */ > + if (cpu_has_hypervisor) { > + up->port.type = PORT_16550A; > + up->capabilities |= UART_CAP_FIFO; > + return; > + } Have you audited vmware, virtualbox, and everyone else that provides a virtual uart device that it will work properly here? qemu isn't all the world :) thanks, greg k-h